Tucked away along the length of a narrow alleyway near St George the Martyr church by Borough tube station is a wall with a gruesome and fascinating past.
It is all that remains of the Marshalsea, one of the most notorious debtors prisons that existed in Borough in various forms for over 500 years.
It was made famous by Charles Dickens who described the atrocious conditions with forensic accuracy in his novel Little Dorrit, but also featured in other novels, The Pickwick Papers and David Copperfield.
He knew of it because his father John, notorious for living above his means, found himself incarcerated there for a few months in 1824 when he couldn't pay his baker's bill of £3500 (in today's money). Now that is a lot of bread, although people were sent here for much lesser amounts.
They weren't really prisons as we would understand them nowadays, more like lodging houses for people that couldn't pay their creditors and people were incarcerated until they had worked off their debt via labour or secured outside funds to pay the balance.
If you got on the wrong side of the jailers, you could end up being tortured with thumbscrews, skullcaps and flung into the 'strongroom' which was a windowless shed near the main sewer, next to piles of night soil and cadavers awaiting burial. If you had some cash, things were a little easier, but it was quite normal to end up living with up to four men living in a room that measured barely more than 10ft square. Often whole families would move in at the same time.
Whilst his father was imprisoned here, Charles Dickens - who was only 12 years old at the time - was made to work for over 10 hours a day in a shoe blacking factory; a mind numbingly tedious and humiliating job that he never forgot and which became a major source of inspiration throughout the rest of his writing career.
Understandably perhaps, he also went on to be keen advocate for prison reform.
He worked at this job for over a year and the journey involved a 5 mile walk every Sunday with his sister to visit him. Eventually he did move closer to Marshalsea, but he did have to walk to his work from there every day.
Later in life, Dickens spoke about his journey over the Blackfriars bridge and his memory of an ironmongers shop with a sign above the door of a dog eating from a bowl. In recognition of this, the sign was recreated on top of a lamppost diagonally opposite Southwark tube station on the eve of his 201st birthday as the culmination of a year of bicentenary events.
To be honest it looks like it could do with a bit of a clean!